Very stable. New, stable releases have been coming out roughlyevery 6 to 18 months since 1991, and this seems likely to continue.Currently there are usually around 18 months between major releases.
With the introduction of retrospective “bugfix” releases the stability ofexisting releases is being improved. Bugfix releases, indicated by athird component of the version number (e.g. 2.1.3, 2.2.2), are managedfor stability; only fixes for known problems are included in a bugfixrelease, and it’s guaranteed that interfaces will remain the samethroughout a series of bugfix releases.
The 2.3.3 release is the most stable version at this point in time.